1. Field of the Invention
The invention relates to a semiconductor device, and a method of producing the semiconductor device. Particularly, the invention is concerned with a technology of increasing the withstand voltage of a semiconductor device having a semiconductor structure (such as a MOSFET structure, IGBT structure or a diode structure) using a trench-type electrode.
2. Description of Related Art
A technology of constructing a semiconductor structure (such as MOSFET, IGBT, or diode) that functions as a semiconductor device, in a semiconductor substrate in which a body region of a first conductivity type (e.g., p-type) is laminated on a surface of a drift region of a second conductivity type (e.g., n-type), has been developed. In this type of semiconductor device, trench-type electrodes may be used. In this connection, there is known a technology of increasing the withstand voltage of the semiconductor device and suppressing or preventing breakdown of the semiconductor device, by increasing the thickness of an insulating film that fills a bottom portion of each trench, so as to relax an electric field in the bottom portion of the trench. The related art as described above is disclosed in, for example, Japanese Patent Application Publication No. 10-98188 (JP 10-98188 A).
However, in the semiconductor device of JP 10-98188 A, too, breakdown may occur when an electric field that is higher than an allowable electric field allowed to be applied to the thick insulating film in the bottom portion of the trench is applied to the insulating layer. In this case, carriers may flow into a gate electrode, through a gate oxide film of the trench-type electrode, and may affect the gate insulating film.